Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <iostream>
#include <queue>
using namespace std;
typedef pair<int, int> P;
int h, w, d[50][50];
int dy[4]={1, 0, -1, 0}, dx[4]={0, 1, 0, -1};
string s[50];
int main() {
    int m=0;
    cin>>h>>w;
    for(int i=0;i<h;i++){
        cin>>s[i];
    }
    for(int i=0;i<h;i++){
        for(int j=0;j<w;j++){
            d[i][j]=1e5;
            if(s[i][j]=='.')m++;
        }
    }
    queue<P> q;
    q.push(P(0, 0));
    d[0][0]=1;
    while(!q.empty()){
        P p=q.front();
        q.pop();
        int y=p.first, x=p.second;
        for(int i=0;i<4;i++){
            int ny=y+dy[i], nx=x+dx[i];
            if(ny>=0&&ny<h&&nx>=0&&nx<w){
                if(d[ny][nx]==1e5&&s[ny][nx]=='.'){
                    d[ny][nx]=d[y][x]+1;
                    q.push(P(ny, nx));
                }
            }
        }
    }
    if(d[h-1][w-1]==1e5){
        cout<<-1<<endl;
    }else{
        cout<<m-d[h-1][w-1]<<endl;
    }
	return 0;
}